Automatic finishing chip process

ABSTRACT

A method of producing finishing chips comprising the steps of providing a castable mixture of particulate abrasive grains and a solidifiable matrix, depositing the mixture into cavities of a generally-cylindrical, flexible mold having a plurality of cavities in the interior surface thereof conforming to the desired configuration of finishing chips to be produced, rotating said cylindrical mold during solidification of said mixture and the production of solid finishing chips within said cavities, and ejecting said solidified finishing chips from said mold by bringing said mold to an inside-out position, whereby said solidified finishing chips are ejected from said cavities, is disclosed. Apparatus which may be employed in carrying out the method, representatively comprising a generally-cylindrical chamber supported on a hollow shaft which is mounted for rotation, a flexible mold disposed within said chamber, and means associated with the bottom of said mold and operative through and within said hollow shaft for positioning said mold in chip-molding location within said chamber or in inside-out chip-ejecting location outside of said chamber, is also disclosed.

This is a division of application Ser. No. 212,754, filed Dec. 4, 1980,now U.S. Pat. No. 4,349,327, issued Sept. 14, 1982.

BACKGROUND OF THE INVENTION

(1) Field of Invention

Tumbling media, finishing media, or finishing "chips" for use in thefinishing of parts or workpieces by intimate contact therewith in afinishing chamber according to centrifugal, vibratory, gyratory, orrotatory motion, or combinations thereof; production of such finishingmedia or chips; apparatus for production thereof; method for theproduction thereof.

(2) Prior Art

The mechanical finishing industry utilizes a wide variety of tumblingmedia, finishing media, or finishing "chips," in a multitude of shapesand forms, for the surface refinement and/or deburring of parts ofworkpieces which are usually of metal or plastic. The proceduresemployed for such surface refinement include centrifugal, vibratory,gyratory, and rotational procedures, and combinations thereof. In theinitial stages of the development of the finishing art, such mediaincluded natural or synthetic stone, porcelain, abrasive filled clays,wood, leather, plastics, and the like. Ceramics have been popular inrecent years, but are gradually being replaced by resin-bonded media dueto cost factors. Whatever the type of finishing media employed, theparts to be refined or deburred are generally placed in a suitablefinishing chamber together with the finishing media, which is of looseparticulate nature, supports the parts, prevents undue collisionthereof, and carries or supplies the abrasive which performs the surfacefinishing or deburring. Incorporation of the particulate abrasivematerial into a resin binder has become popular because the size andshape of the finishing chip can, in such case, be varied widely to suitindividual requirements for dimensions, hardness, and the like, not onlyof the resin binder but also of the abrasive material incorporatedtherein. Precisely uniform shapes are attainable in the production ofsuch media, but high-density chips, free of air bubbles, having minimumflash, and which are readily mass produced and simply and completelyejected from the mold in which made with a minimum of labor, for obviouspurposes of economy, have not heretofore been available. Up until thepresent time, resin-bonded finishing chips have usually beenindividually cast or molded, with obvious disadvantages. Procedure forthe production of ceramic or polymeric media by drop-wise feeding ofthixotropic compositions from an orifice and thereafter hardening thesame has been provided according to the procedure of U.S. Pat. No.3,549,341, which goes into great detail concerning previous methods anddisadvantages thereof. A continuous method of making abrasive finishingmedia or chips is also disclosed in U.S. Pat. No. 3,503,725, whichinvolves the movement of gelatinous or uncured finishing material alonga moving web, cutting the mass into suitable segments, and curing theindividual segments to produce abrasive chips. Although both of thesemethods provide advantages over prior art procedure involving theindividual molding or casting of pastelike ceramic or resin-bondedabrasive compositions, they still leave much to be desired from thestandpoint of economy, flash reduction, elimination of air bubbles, andmass production of high-quality chips in a simple and convenient manner.Alternative existing procedure for the molding of finishing chipssuffers from even greater disadvantages of excessive flash, excell laborcosts, and incomplete ejection from the mold wherein produced. It isobvious that a simpler, more expeditious, and more economically-feasiblemethod of mass producing finishing chips would be highly desirable andadvantageous to the finishing industry. Such is provided according tothe method and apparatus of the present invention, whereby high-densityfinishing chips, free of air bubbles and having a minimum of flash, maybe readily mass produced and simply, completely and automaticallyejected from the mold in which made with a minimum of labor and with amaximum of economy.

SUMMARY OF THE INVENTION

In summary, the invention comprises a method of producing finishingchips comprising the steps of providing a castable mixture ofparticulate abrasive grains and a solidifiable matrix, depositing themixture into cavities of a generally-cylindrical, flexible mold having aplurality of cavities in the interior surface thereof conforming to thedesired configuration of finishing chips to be produced, rotating saidcylindrical mold during solidification of said mixture and theproduction of solid finishing chips within said cavities, and ejectingsaid solidified finishing chips from said mold by bringing said mold toan inside-out position, whereby said solidified finishing chips areejected from said cavities, and such a method wherein castable mixtureis deposited into the mold interior in a fluid, gelatinous, orsemi-solid state, wherein a pre-measured amount of castable mixture isdistributed about the mold interior by rotation of the mold, whereincastable mixture is distributed about the mold interior with theassistance of a doctor blade, wherein castable mixture is solidified byapplication of heat, by air drying, or catalytically, wherein both moldcavities and finishing chips are tapered so as to provide a greaterdimension at the chip base than at its top, wherein mold cavities andchips are generally triangular, conical or pyramidal, wherein saidflexible mold is of rubber or elastomeric material and wherein saidchips are ejected from said cavities by deforming said cavities so as toassume a greater dimension during the ejection step than during themolding step, wherein said solidified finishing chips are ejected fromsaid mold while rotating said mold, wherein said mold is brought to aninside-out position by mechanical means, wherein said mold is brought toan inside-out position by means comprising mechanical means andhydraulic means, wherein said mold is brought to an inside-out positionby means comprising pneumatic means, wherein said mold is restrainedwithin a generally-cylindrical wall during solidification of saidmixture, wherein said cylindrical mold is positioned as an inner liningof said cylindrical chamber during the chip-production step, whereinsaid mold is brought to an inside-out position outside of saidgenerally-cylindrical wall for ejection of solidified chips from saidcavities, wherein said mold has a bottom and is brought to an inside-outposition outside of said cylindrical wall by pushing the bottom thereofoutside of said cylindrical wall, wherein said mold has a bottom and isbrought to an inside-out position outside the said cylindrical wall byexertion of air pressure against the bottom of said mold, wherein saidcylindrical wall constitutes a portion of a generally-cylindricalchamber and said chamber is rotated about its central axis for rotationof said cylindrical mold therein, wherein said chip is a resin-bondedchip and said castable mixture is a mixture of solidifiable resincontaining abrasive grains therein, and wherein said resin-bonded chipis a urea-formaldehyde resin-bonded chip and said castable mixturecomprises an acid-catalyzed urea-formaldehyde resin and abrasive grainmixture.

The invention in summary also comprises apparatus which may be employedin carrying out the aforesaid method and suitable for the production ofloose, particulate finishing chips for use in effecting vibratory,centrifugal, gyratory, or tumbling type finishing or the like,comprising: a generally-cylindrical wall mounted for rotation about acentral axis, means for rotating said wall about said axis, agenerally-cylindrical sheetform flexible mold, having a plurality ofcavities therein conforming to the desired configuration of thefinishing chips desired to be produced, affixed to said wall at theouter periphery thereof and adapted to be located in one of twolocations, the first of which locations is inside of said wall andadjacent the inside surface of said wall, in which location said wall isin mold-supportive position and said mold is in chip-molding position,and the second of which locations is an inside-out location generallyoutside of said wall and extending outwardly from the periphery thereof,in which location said mold is in chip-ejecting position, and means formoving said flexible mold from said first location to said secondlocation and vice-versa, and such apparatus wherein said wall issupported on a shaft, and including means supporting said shaft forrotation and means for driving said shaft, wherein said wall is a partof a chamber including a bottom, wherein said mold constitutes an innerlining of said wall when in said first position and is not attachedinternally inside of said cylindrical wall, wherein said flexible moldis of rubber or elastomeric material, wherein said rubber or elastomericmaterial is of such a nature as to impart the cavities therein in saidfirst location with one dimension and in said inside-out location with agreater dimension, wherein said flexible mold is of silicone rubber,wherein said mold is provided with a bottom, wherein the means formoving said mold from said first location to said second location andvice-versa comprise mechanical means, wherein said mechanical means areactuated by associated hydraulic means, wherein said means for movingsaid mold from said first location to said second location andvice-versa comprise pneumatic means, wherein said shaft is a hollowshaft, wherein said wall is a part of a chamber having a bottom, saidhollow shaft is affixed to said chamber bottom, and wherein saidflexible mold is itself provided with a bottom, wherein said means formoving said mold comprise an inner shaft movable longitudinally withinsaid hollow shaft, attached to said mold bottom, and adapted to beactuated to move said mold from said first position to said secondposition and back again, wherein said inner shaft is adapted to be movedby hydraulic means associated with said shaft, wherein longitudinalmovement of said inner shaft is controlled by means of a thrust collaron said inner shaft, wherein said inner shaft is adapted to rotate alongwith said outer hollow shaft, wherein counterbalance means is affixed tosaid hollow shaft on the opposite side of said support means from saidchamber, wherein said means for moving said mold comprise pneumaticmeans associated with said hollow shaft for generating pressure orvacuum through said hollow shaft and against said mold bottom, andwherein said chamber comprises a perforated baffle adjacent but spacedfrom its bottom for support of said mold bottom.

In summary, the apparatus may be more generally referred to ascomprising a generally-cylindrical flexible mold having a plurality ofcavities in the interior surface thereof conforming to the configurationof chips to be produced, means for rotating said mold duringsolidification of said mixture and production of solid finishing chipswithin said cavities, and means for ejecting said solidified finishingchips from said mold by bringing said mold to an inside-out position,whereby said chips are ejected from said cavities, preferably: said moldbeing restrained within a generally-cylindrical wall supported forrotation, said mold having a bottom and said ejecting means comprisingmeans for bringing said mold to an inside-out position outside of saidwall by pushing the bottom thereof outside of said wall or by exertionof air pressure against said mold bottom, said wall constituting aportion of a chamber having means for rotation about its central axisfor rotation of said mold therein, said mold being of rubber orelastomeric material of such a nature as to impart the cavities thereinwith one dimension during solidification and production of chips andwith a greater dimension in inside-out ejecting position, and said moldcavities being tapered so as to provide a greater dimension at the chipbase than at its top.

OBJECTS OF THE INVENTION

Objects of the invention are to provide: an improved method andapparatus for the mass-production of finishing chips or pellets; suchmethod and apparatus which involve the centrifugal casting of finishingchips in a substantially sheetform mold comprising a plurality of moldcavities within which the chips solidify, harden, or cure during thecentrifugal casting operation; such method and apparatus wherebysolidified chips are ejected from mold cavities by turning the mold"inside-out"; such method and apparatus wherein the said ejection ofsolidified chips can be effected automatically; such method andapparatus whereby high-density chips, free of air bubbles and having aminimum of flash, may be readily mass-produced and simply, completelyand automatically ejected from the mold in which made, all with aminimum of labor and a maximum of economy. Other objects of theinvention will become apparent hereinafter and still others will beobvious to one skilled in the art.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The invention, in several preferred embodiments, is illustrated by theaccompanying drawings, in which:

FIG. 1 is a partial cross-sectional view of apparatus according to theinvention, taken along line I--I of FIG. 4, in make-ready stage, showinga flexible mold with compound-containing cavities therein.

FIG. 2 is a partial cross-sectional view of a flexible mold according tothe invention in reversed or "inside-out" position, taken along lineII--II of FIG. 4, showing ejection of finishing chips therefrom.

FIG. 3 is a perspective view of a finishing chip or pellet producedaccording to the invention.

FIG. 4 is a side view, partially broken away and partially in section,of a centrifugal casting apparatus according to the invention.

FIG. 5 is a side view, partially in section, of alternative centrifugalcasting apparatus according to the invention.

FIG. 6 is an enlarged cross-sectional view of a mold cavity in aflexible mold according to the invention in molding position withfinishing chip therein.

FIG. 7 is an enlarged cross-sectional view of a mold cavity in aflexible mold according to the invention in ejection position withfinishing chip being ejected therefrom.

FIG. 8 is a key to the dimensions a through d employed in FIGS. 6 and 7.

SPECIFIC REFERENCE TO THE DRAWINGS

Reference is now made to the accompanying drawings for a betterunderstanding of the invention, wherein all the essential parts arenumbered and wherein the same numbers are used to refer to correspondingparts, or wherein the same numbers but differing by a factor ofone-hundred (100) are used to refer to corresponding parts.

In a preferred form, the apparatus of the invention is shown in FIG. 4.An alternative apparatus, which employs pneumatic means for ejection ofthe formed finishing chips from the flexible mold, rather thanmechanical means, is shown in FIG. 5. The rotatable chamber, withinwhich the flexible mold according to the invention is located, when theapparatus is in molding position, is shown generally in FIGS. 4 and 5 at10 and 110. The rotatable chamber, which is rotatable about its centralaxis, is shown in the form of an open-ended annular drum havingmold-supportive sidewalls 13 and 113. Such drum may representativelyhave an internal diameter of slightly more than sixty (60) inches (1524millimeters) to accommodate the essentially sheet-form flexible mold ofapproximately such dimensions within the interior chamber thereof. Inmolding position, shown in unbroken lines in FIG. 4, the flexible mold11 is located inside drum 10, lies closely adjacent to mold-supportivedrum wall 13, and is advantageously provided with bottom 17. As shown inchip-ejecting position in FIG. 4 by dotted lines, when ejecting formedand solidified finishing chips, the flexible mold 11 is extendedoutwardly from the outer rim or periphery of drum 13, to which it isattached along its circumference, then being in inside-out condition,with the mold cavities 12 facing outwardly, rather than inwardly as isthe case when mold 11 is in molding mode or position within drum 10.

As shown in FIG. 1, which is a cross-section taken along line I--I ofFIG. 4, in molding position the flexible mold 11 of the invention liesclosely adjacent to mold-supportive wall 13 of drum 10. As the drum isrotated about its central axis, a pre-measured amount of compound 14,comprising a mixture of matrix and abrasive, is introduced into themold. Since the compound 14 is generally in semi-solid, gelatinous, orfluid condition at this point and has a viscosity which allows it tomove readily within the mold interior, to the surface of which itadheres due to the centrifugal force imparted by rotation of drum 10, itlocates itself conveniently and rapidly within mold cavities 12. Asshown in FIG. 1, a scraper or "doctor" blade located interior of therotating chamber 10 may be used to assist in the more convenient andrapid location of compound 14 within the mold cavities 12 and for theremoval of any excess compound 14 which may be present.

After completion of the rotation and molding or casting cycle, duringwhich the compound 14 is compressed into the mold cavities 12 bycentrifugal force, and allowed to solidify, the flexible mold 11 isturned inside out for ejection of the hardened finishing chips orpellets 15 from the mold cavities 12.

During the rotation of molding stage, the centrifugal force generated bythe rotation is able to exert its full force and effect upon thehardening chips 15 in cavities 12 due to the mold-supporting or "backup"effect of wall 13 which lies in juxtaposition to and in contact withflexible mold 11.

As shown in FIGS. 6 and 7, and as explained in the key of FIG. 8, whenthe flexible mold 11 with its plurality of mold cavities 12 is inmolding position, the base "a" of the chip is compressed within base "b"of the mold cavity 12, which is essentially of the same dimensions asthe base "a" of the finishing chip being formed. As shown, the finishingchip is of pyramidal shape, having a greater circumference at its basethan at its top, and has a height identified as "d". Conversely, whenthe flexible mold of the invention is in ejecting position, as seen inFIG. 7, due to the flexibility of the mold material employed, which ispreferably natural or synthetic rubber or other elastomer, especiallywhen under pressure or when rotating, the finishing chips or pellets 15are readily disengaged from the mold cavities 12, inasmuch as the outerdiameters "c" constituting the bases of the mold cavities 12 assumedimensions larger than "b" for ready and convenient ejection of thesolidified and hardened finishing chips from the mold cavities 12.

FIG. 2 shows the ejection of finishing chips or pellets 15 from the moldcavities 12 in flexible mold 11 during an ejection cycle, FIG. 2constituting a cross-sectional view of the "inside out" mold along lineII--II of FIG. 4.

FIG. 3 shows a conical or pyramidal finishing chip or pellet 15 producedaccording to the present invention, having a greater diameter across itsbase "a" than at its top and having a height "d", as more particularlyshown in FIGS. 6 and 7. This particular configuration of finishing chipor pellet, while preferred, is only one of innumerable shapes or formswhich may be conveniently produced according to the method of theinvention and using the apparatus of the present invention.

FIG. 4 shows in detail and partial schematic a complete apparatus of thepresent invention which may be employed for the convenient production offinishing chips or pellets. A rotatable chamber in the form of anopen-ended cylindrical drum is generally shown at 10 and has sidewall 13and bottom 16 supported by radial supports 23, central core 24, andappropriate weldments. Sidewall 13 has flange 21, to which is attachedcorresponding flange 22 of the flexible mold 11 which, when in moldingmode or position, in effect constitutes an inner lining of the drum 10.Flexible mold 11 is secured to bottom 17, thereby constituting an entireinner lining for drum 10 when in interior molding mode or position. Drum10 is secured by central core 24 to hollow outer shaft 26, which isjournaled for rotation in bearings not shown in the interior of theupper section of stanchion 27 which, along with stanchion 37, supportsthe apparatus as a whole. Outer hollow shaft 26 carries pulley 28affixed thereto which, together with pulley 29, connecting belt 30, anddriving motor 21, provides the means for rotating shaft 26 and drum 10carried thereby. Counterbalance 32 is shown affixed to the opposite endof shaft 26 for counterbalancing drum 10 at the other side of stanchion27.

Mold bottom 17 is securely affixed to interior shaft 33, which isseparated interiorly from outer hollow shaft 26 by seal 25, but which issecured for rotation together with hollow outer shaft 26 bycorresponding interlocking of mutually engaging means not shown on theoutside of inner shaft 23 and the inside of outer shaft 26. At the endof inner shaft 33 opposite the end secured to the bottom 17 of mold 11is affixed thrust collar 34, in turn associated with two-way hydraulicthrust and return means 35, 36, and 38, in turn connected by hoses 39and 40 to a fluid source not shown and associated switches foractivating the same either for outward thrusting for chip ejection orreturn for a further molding cycle.

The dotted lines in FIG. 4 show the flexible mold 11 of the invention inejecting mode or position, with inner shaft 33 and mold bottom 17 thrustoutwardly to the full extent enabled by thrust collar 34 for the purposeof ejecting the solidified and hardened finishing chips or pellets fromthe cavities 12 of mold 11, and show the finished chips 15 beingcollected en masse in a suitable container.

In the alternative structure shown in FIG. 5, flexible mold 111 havingmold cavities 112 is shown secured to open-ended drum 110 by means ofrivets 122 along peripheral flange 121 extending entirely around thecircumference of drum 110 at the outer edge of wall 113. As shown insolid lines, the mold is in ejecting position. Dotted lines show theflexible mold 111 in molding mode or position, in which mode theflexible mold lies closely against wall 113 of drum 110 and, with itsbottom 117, forms a complete inner lining for drum 110. Bottom 117 liesin molding mode against baffle 119 having openings 120 therethrough,which baffle is secured by circular brace 118 to drum bottom 116, whichis in turn secured to hollow shaft 126 by radial supports 123 andappropriate weldments. Hollow shaft 126 is journaled in two-way thrustbearings, not shown, in the upper portion of stanchion 127, whereas theopposite end of hollow shaft 126 is lodged in seal 141 at the upperextremity of stanchion 137. Said seal, while permitting rotation and abuildup of pressure within hollow shaft 126, also prevents theinadvertent or accidental creation of air currents or vacuum withinhollow shaft 126. Pulley 128 and associated belt 130 are in turnassociated with a motor and additional pulley, not shown, for rotationof shaft 126 and drum 110 secured thereto, as well as counterbalance 132secured to shaft 126 on the other side of stanchion 127. Fluid connector142 leads into seal 141 and attached hosing 143 is associated with asource of air and vacuum and appropriate switch means, not shown.

According to the embodiment shown in FIG. 5, flexible mold 111 is turnedinside out by the employment of air pressure released through hosing143, connector 142, seal 141, and along hollow shaft 126, throughopenings 120 in baffle 119, thereby forcing flexible mold 111 from itsmolding mode or position into its ejecting position, as shown in FIG. 5.In contrast to the apparatus of FIG. 4, the means for forcing theflexible mold into ejecting position is entirely of a pneumatic nature,rather than of a mechanical nature, namely, the interior pusher orpiston rod 33 and associated bottom 17 of the apparatus shown in FIG. 4.Whereas, in the apparatus of FIG. 4, for replacement of the flexiblemold into a further molding mode or position, it is only necessary toactivate the hydraulic means to return position, thereby retractinginterior pusher or piston rod 33 and bringing the flexible mold 11 backinto a "lining" or molding mode or position, according to the embodimentof FIG. 5 this same effect is produced simply by switching from airpressure to vacuum, which in turn reverses the flow of air through seal141 and in hollow shaft 126, whereby bottom 117 of flexible mold 111 issuctioned back into "lining" or molding mode or position againstsidewall 113 and baffle 119 of the rotatable drum 110.

OPERATION OF THE APPARATUS

In operation, the fluid, gelatinous, or semi-solid mixture of matrix andabrasive, i.e., compound 14, is loaded into the interior of drum 10 or110 with the flexible mold 11 or 111 in "lining" position interiorthereof and ready for the molding operation. The amount of mixture orcompound 14 is conveniently pre-measured and is generally readilydistributed in the liquid or viscous state into mold cavities 12 or 112.This distribution and the removal of any excess may be facilitated bythe employment of a doctor blade such as 16, as shown in FIG. 1, whichmay be inserted into the interior of drum 10 or 110 and which may behand held, otherwise supported, or automatic, according to usualprocedure for the employment of doctor blades, as is well known in theart. Whether the mixture or compound 14 is to be cured by air drying,catalyzation, or heat, or combinations of the same, it is in any event acastable material of sufficient fluidity and adequate viscosity toenable ready distribution within the flexible mold 11 or 111 uponrotation of the drum 10 or 110, with or without the employment of adoctor blade such as 16. Upon rotation of the chamber 10 or 110,containing the flexible mold 11 or 111 in molding position therein, fora sufficient period, e.g. for fifteen (15) minutes, the finishing chipsor pellets 15 within mold cavities 12 or 112 are sufficiently set orcured so that the ejection cycle can be commenced. This ejection cyclecan be carried out easily with drum 10 or 110 either in stationary or inrotating condition, with the ejection being somewhat more controllablewhen it is carried out with the drum in stationary or relativelystationary condition. On the other hand, when ejection is carried outwith drum 10 or 110 rotating, the ejection of pellets 15 from moldcavities 12 or 112 is considerably faster and more complete.

In any event, at the end of the molding cycle, flexible mold 11 or 111is turned inside out and brought to its second or ejection position,thereby to eject the solidified finishing chips or pellets 15 from moldcavities 12 or 112, whereupon they may be caught in a suitable containeras shown, deposited upon an endless belt, or collected in any othersuitable manner. If additional time is required for curing, this can beprovided after ejection of the solidified finishing chips or pellets 15from the mold. As shown, these pellets 15 are tapered from their bottomto their top to facilitate ejection from the mold and, also as shown ,are in pyramidal shape or form. Such shapes or forms wherein thefinishing chips are tapered from their base to their top are preferredfor obvious reasons of facilitating ejection from the mold, althoughinnumerable other shapes or forms may be imparted to the finishing chipor pellets with facility depending only upon the shape of the moldcavities 12 or 112. Ejection from the mold presents no problem,requiring only that the flexible mold 11 or 111 be sufficiently flexibleto eject the solidified finishing chip or pellet therefrom after moldingand solidification thereof.

Flexible mold 11 or 111 can, of course, be turned inside out and/orreturned to its "lining" and molding position within the drum 10 or 110by hand, if desired, with some inconvenience or by using an appropriatehandle not shown which is attached or attachable to the bottom of themold 17 or 117, or in any other suitable manner, but the means shown inFIGS. 4 and 5 and previously described is far preferable and has provedextremely useful in practice.

The flexible mold may, as previously stated, be of any desiredcomposition, such as natural or synthetic rubber or other elastomer, orany other flexible material suitable for the formation of a plurality ofmold cavities therein. A material such as silicon rubber has been foundto be extremely useful in practice. The material should, of course,according to the preferred embodiment of the invention, be of sufficientflexibility so that, when in the ejection mode for ejection ofsolidified finishing chips or pellets therefrom, especially uponrotation and/or under pressure from within, the mold cavities located inthe surface thereof assume greater dimensions than they possessoriginally, e.g., when they are in the molding position, thereby tofacilitate ejection of the solidified finishing chips or pellets fromthe mold cavities. Thus, as shown in FIGS. 3, 6, and 7, the diameter ofthe mold cavities during ejection is larger than their original diameterduring molding, with the effect that this increase in circumferenceactually serves to "pop-out" the solidified finishing chips or pelletsfrom the cavities during the ejection mold or step.

According to the embodiment shown in FIG. 4, after completion of themolding, including solidification, cycle, for conversion into theejection cycle, hydraulic means 35, 36, 38 is activated, thereby forcinginner shaft 33, affixed to flexible mold bottom 17, through seal 25 andlongitudinally within outer hollow shaft 26 to the full extent permittedby thrust collar 34, thereby forcing flexible mold 11 and its bottom 17into the position shown by dotted lines in FIG. 4. After all finishingchips or pellets 15 are ejected, the "inside ou" flexible mold 11 isthen returned to its "lining" or molding position by simple reversal ofhydraulic means 35, 36, and 38, thereby reversing the path of travel ofinner shaft 33 inside of outer hollow shaft 26, to its originalposition, thereby returning flexible mold bottom 17 to its originalposition within drum 10 adjacent to drum bottom 16. In this position,flexible mold 11 and its ancillary equipment for the centrifugal castingof finishing chips or pellets 15 is ready for commencement of a furthermolding operation.

According to the embodiment shown in FIG. 5, for ejection of finishingchips or pellets 15 from the cavities 112 of flexible mold 111, the sameprocedure is employed. In the position shown in solid lines in FIG. 5,the flexible mold 111 and its bottom 117 are shown in extended orejection position, outside of drum 110. This position is attained aftercompletion of a suitable molding, including solidification, cycle,merely by activating air flow through bore 143, connector 142, seal 141,and through the interior of hollow shaft 126. The air pressure thusgenerated proceeds into drum 110 and through openings 120 in baffle 119against the bottom 117 of flexible mold 111, forcing it outwardly intoejecting position as shown in solid lines in FIG. 5. According to thisembodiment, when it is desired to reinstitute the molding cycle andreturn the flexible lining 111 into "lining" or molding position withindrum 110, it is a simple matter to switch hose 143 to a source ofvacuum, thereby providing through connector 142, seal 141, and hollowshaft 126 a vacuum which operates through openings 120 in baffle 119 andagainst flexible mold bottom 117 in precisely the reverse order, bottom117 thereby being drawn back within walls 113 of drum 110 and being oncemore located against baffle 119 and walls 113 for commencement ofanother molding cycle.

Thus, the difference between the embodiments of FIG. 4 and FIG. 5 isfundamentally that the embodiment of FIG. 4 employs mechanical means,namely, inner shaft 33 attached to movable bottom 17 of the flexiblemold for purposes of ejection, whereas the embodiment of FIG. 5 employspneumatic means, namely, either air pressure or vacuum, for moving theflexible mold 111 and its bottom 117 into ejecting position andrestoring it to a "lining" or molding position, respectively, theoperation of the two embodiments being otherwise essentially the same.

The following specific example is given by way of illustration only, andis not to be construed as limiting.

A fluid compound or mixture of abrasive grains and matrix was preparedby mixing ten (10) micron silica into a urea-formaldehyde resin in theliquid state, which was subsequently catalyzed with an acid in the usualmanner for solidification of urea-formaldehyde resins. The mixture wasthen poured into a rotating flexible mold in the apparatus depicted inFIG. 4, the interior of which mold was lightly scraped with a doctorblade for one minute to distribute the mixture uniformly into the moldcavities throughout the full inner circumference of the mold. Therotation of the mold within the drum was continued for a period offifteen (15) minutes, whereafter the mold was turned inside out aspreviously described for ejection of the solidified finishing chips orpellets. In a test conducted while the flexible mold was rotating insideof its supporting rotating drum, the ejection was extremely rapid andcomplete. In a further test, wherein the rotation was stopped prior toejection, the elapsed time for ejection was greater and the degree ofejection was less complete. In both cases, however, the finishing chipsor pellets were readily ejected in a sufficiently solidified state sothat they could be readily collected and allowed to air cure over afurther extended period.

The finishing chips or pellets thus prepared were found to be entirelysuitable for use in the finishing of parts, for example, for finishingthe surface of zinc die castings by either tumbling or vibratoryfinishing, as in a Spiratron® helical vibratory finishing device or in acentrifugal finishing device such as the Rotomax™. The production ofadditional embodiments of finishing chips according to the presentprocess and in the present apparatus results in chips of a similarnature suitable for employment in finishing the surfaces of variousparts including aluminum castings, aluminum machined parts, varioussteel machined parts, steel stampings, punchings and forgings, ceramics,and the like. The size of the representative pyramidal chips produced inthe foregoing example and employed as set forth in the foregoing is 3/8inch diameter at base×5/16 inch in height, although innumerable othershapes and sizes can be produced, including, for example, triangles11/2"×3/4"×1/2", 11/2"×3/4"×1/4", 7/8"×7/16"×1/4", et cetera, as well asvarious other shapes and forms other than pyramidal or conical, such asspherical or cylindrical, and having numerous other cross-sections,e.g., elliptical, rectangular, circular, or triangular, as typicalexamples, it being understood that forms or shapes having greaterdimensions at their bases than at their top or apex are preferred froman ease of ejectment standpoint.

In cases where a heat cure is desirable, it has been found thatsolidification and curing of the finishing chips or pellets can befacilitated by directing a stream of hot air interior of the flexiblemold inside its rotating drum during the molding and curing procedure.Alternatively, after ejection of solidified finishing chips or pellets,the same can be subjected to a stream of hot air on a movable belt froman overhead source, if desirable, for a complete and extremely rapidcure. Alternatively, in the production of finishing chips involvingcatalytic reaction or simple air drying, the cure may be effectedcompletely by or during the centrifugal casting process within the drumwhile rotating, without the necessity for continued air drying orapplication of heat.

In all cases, the finishing chips or pellets produced have been found tobe of uniform nature, of high density and without air bubbles, and ofhigh quality, with little or no scrap or flash being produced due to thepossibility of introducing predetermined amounts of the compound ormixture into the mold. Perhaps the greatest advantage of the presentprocess and apparatus is one of economics, since an extremely smallamount of labor is involved. Such scraping as may be necessary ordesirable in carrying out the molding operation is not time consuming,inasmucn as a predetermined amount of the compound or mixture can beintroduced into the mold and because the mixture distributes itselfrapidly into the mold cavities due to its suitable viscosity androtation of the mold itself, whereas ejection of the finishing chips orpellets from the mold can be entirely automatic, as previouslydescribed, and can even be computer-programmed so as to be carried out apredetermined time after the commencement of each molding cycle.

It is clear that the method of the invention and the apparatus of theinvention can be employed not only with urea-formaldehyde systems, butthat it can also be employed with polyester systems, or any other systeminvolving a castable material or matrix which, when considered as a"compound" together with the abrasive grains therein, can be cast in thefluid, gelatinous, or semi-solid state, and which will heat cure, dry,or catalyze to solidify, harden, set, or cure. It is obvious that anysuitable kind of abrasive grain may be employed in producing thefinishing chips or pellets according to the invention, such as, forexample, innumerable silica sand, aluminum oxide, silicon carbide,bauxite, vocanic ash, or tripoli abrasive grains, or the like. Althoughthe method and apparatus of the invention can be employed with anycastable system, whether ceramic, plastic, or otherwise, it should beapparent that a preferred embodiment thereof involves the casting ofplastic-bonded finishing media of the type now extremely popular in thedeburring, cleaning, descaling, burnishing, finishing, and polishing ofparts or workpieces in centrifugal, vibratory, gyratory, or rotating(tumbling) apparatus, or an apparatus providing a combination of suchactions, all as previously stated.

By "finishing material", "finishing media," "finishing medium,""finishing chips," or "finishing pellets," as these terms may be usedinterchangeably herein, it is intended to include such materials asexemplified by FIG. 3 hereof, which serve as loose, particulate, andsolid finishing materials of the type presently employed in the tradeand others of a similar nature. Moreover, these terms are used hereingenerally to designate such solid materials which are used to impart alltypes of finishes including those finishes acquired with abradingmaterials as well as with polishing materials, polishing beingconsidered in its usual sense as one species of finishing.

The method and apparatus of the present invention have many advantagesover conventional procedure and equipment of the art. Among these arethe following: uniform chips of high density and without the presence ofair bubbles, a major problem especially with small chips, and of thehighest quality due to effective centrifugal force during casting:little or no scrap or flash, due to the possibility of employingpredetermined amounts of matrix-abrasive mixture in each molding cycle;and extremely good economics, in view of the absence of manual laborrequirements, loading and scraping to the extent necessary beingextremely rapid because of the ability to employ predetermined amountsof abrasive-matrix mixture and rapid distribution of compound within themold and mold cavities even without scraping due to rotation of themold, whereas ejection is automatic.

Although the flexible mold as shown in the drawings is supported by acylindrical wall mounted for rotation about a central axis, in the formof a cylindrical chamber supported on a shaft for rotation, with meanssupporting the shaft for rotation and means for driving the shaft forrotation of the chamber wall, numerous modifications may be made withoutdeparting from the invention. It is only necessary that the cylindricalflexible mold be rotated during solidification of compound therein forproduction of solid finishing chips within the mold cavities, and it isonly necessary in the apparatus of the invention that the cylindricalwall be capable of rotation about a central axis by any suitable means.Although the cylindrical wall supporting the cylindrical sheetformflexible mold in the apparatus of the invention provides considerablesupport for the exterior surface of the flexible mold, so thatcentrifugal force imparted by rotation can exert its full force andeffect upon compound in the mold cavities, thereby permitting attainmentof highest density and elimination of air bubbles from the compound andthe corresponding finishing chips produced, this is a preferredembodiment which is not always essential to the method of the invention.

In addition, although the flexible mold shown and described is always"generally cylindrical", as is any surrounding wall, it is not essentialthat the mold, the surrounding wall, or the chamber of which saidsurrounding wall may be a part, be cylindrical in any precise usualsense of the term. It is only necessary that the flexible mold and anysurrounding wall be "generally cylindrical," that is, insufficientlycornered so as to prevent the free flow of starting fluid, gelatinous,or semi-solid compound or mixture therein and around the interior of themold. For example, the generally-cylindrical flexible mold, anysurrounding wall, and any chamber of which the wall is a part, may havea decagonal, octagonal, hexagonal, or pentagonal cross-section, or anyother cross-section which does not detract from itsgenerally-cylindrical nature or interfere with the flow of compound ormixture about the interior of the mold for rapid filling of the moldcavities therein or with rotation thereof about an essentially centralaxis. Although for purposes of ultimate convenience and operatingefficiency a true cylinder is preferred, other generally-cylindricalmolds and supporting walls may be employed with equal or only somewhatreduced efficiency, as will be apparent to one skilled in the art.

When the mold is herein referred to as being brought to "an inside-outposition" for purposes of ejecting solidified finishing chips from thecavities of the said mold, it is to be understood that said inside-outcondition may be either complete or partial, depending upon the exactmanner of operation desired. It is obvious that the mold is not turnedcompletely inside out in the sense that it generally remains attached tothe outer periphery of the supporting wall, when the apparatus of theinvention is employed, and that the mold may be pushed or forced onlypartially as well as nearly completely from within the confines of anysupporting wall wherein it resides during the molding operation. In anyevent, it is to be understood that the inside-out position of the moldfor chip-ejection purposes may be any desired degree of reversal frompartial to complete, as at the time may appear desirable to the operatorof the method or apparatus of the invention.

It is to be understood that the invention is not to be limited to theexact details of construction, operation, or exact materials orembodiments shown and described, as obvious modifications andequivalents will be apparent to one skilled in the art, and theinvention is therefore to be limited only by the full scope of theappended claims.

I claim:
 1. Method of producing finishing chips comprising the steps ofproviding a castable mixture of particulate abrasive grains and asolidifiable matrix, depositing the mixture into cavities of a generallycylindrical flexible mold having a plurality of cavities in the interiorsurface thereof conforming to the desired configuration of finishingchips to be produced, rotating said cylindrical mold duringsolidification of said mixture and the production of solid finishingchips within said cavities, and ejecting said solidified finishing chipsfrom said mold by bringing said mold to an inside-out position, wherebysaid solidified finishing chips are ejected from said cavities.
 2. Themethod of claim 1, wherein castable mixture is deposited into the moldinterior in a fluid, gelatinous, or semi-solid state.
 3. The method ofclaim 2, wherein a premeasured amount of castable mixture is distributedabout the mold interior by rotation of the mold.
 4. The method of claim3, wherein castable mixture is distributed about the mold interior withthe assistance of a doctor blade.
 5. The method of claim 2, whereincastable mixture is solidified by application of heat, by air drying, orcatalytically.
 6. The method of claim 1, wherein both mold cavities andfinishing chips are tapered so as to provide a greater dimension at thechip base than at its top.
 7. The method of claim 6, wherein moldcavities and chips are generally triangular, conical or pyramidal. 8.The method of claim 1, wherein said flexible mold is of rubber orelastomeric material and wherein said chips are ejected from saidcavities by deforming said cavities so as to assume a greater dimensionduring the ejection step than during the molding step.
 9. The method ofclaim 1, wherein said solidified finishing chips are ejected from saidmold while rotating said mold.
 10. The method of claim 1, wherein saidmold is brought to an inside-out position by mechanical means.
 11. Themethod of claim 1, wherein said mold is brought to an inside-outposition by means comprising mechanical means and hydraulic means. 12.The method of claim 1, wherein said mold is brought to an inside-outposition by means comprising pneumatic means.
 13. The method of claim 1,wherein said mold is restrained within a generally cylindrical wallduring solidification of said mixture.
 14. The method of claim 13,wherein said cylindrical mold is positioned as an inner lining of saidcylindrical chamber during the chip-production step.
 15. The method ofclaim 13, wherein said mold is brought to an inside-out position outsideof said generally cylindrical wall for ejection of solidified chips fromsaid cavities.
 16. The method of claim 13, wherein said mold has abottom and is brought to an inside-out position outside of saidcylindrical wall by pushing the bottom thereof ouside of saidcylindrical wall.
 17. The method of claim 13, wherein said mold has abottom and is brought to an inside-out position outside the saidcylindrical wall by exertion of air pressure against the bottom of saidmold.
 18. The method of claim 13, wherein said cylindrical wallconstitutes a portion of a generally cylindrical chamber and saidchamber is rotated about its central axis for rotation of saidcylindrical mold therein.
 19. The method of claim 2, wherein said chipis a resin-bonded chip and said castable mixture is a mixture ofsolidifiable resin containing abrasive grains therein.
 20. The method ofclaim 19, wherein said resin-bonded chip is a urea-formaldehyderesin-bonded chip and said castable mixture comprises an acid-catalyzedurea-formaldehyde resin and abrasive grain mixture.